mirror of
https://github.com/typst/typst
synced 2025-05-14 04:56:26 +08:00
100 lines
3.3 KiB
Rust
100 lines
3.3 KiB
Rust
use super::prelude::*;
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/// `pad`: Pad content at the sides.
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pub fn pad(_: &mut EvalContext, args: &mut Args) -> TypResult<Value> {
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let all = args.find();
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let left = args.named("left")?;
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let top = args.named("top")?;
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let right = args.named("right")?;
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let bottom = args.named("bottom")?;
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let body: Node = args.expect("body")?;
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let padding = Sides::new(
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left.or(all).unwrap_or_default(),
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top.or(all).unwrap_or_default(),
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right.or(all).unwrap_or_default(),
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bottom.or(all).unwrap_or_default(),
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);
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Ok(Value::block(body.into_block().padded(padding)))
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}
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/// A node that adds padding to its child.
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#[derive(Debug, Hash)]
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pub struct PadNode {
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/// The amount of padding.
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pub padding: Sides<Linear>,
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/// The child node whose sides to pad.
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pub child: PackedNode,
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}
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impl Layout for PadNode {
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fn layout(
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&self,
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ctx: &mut LayoutContext,
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regions: &Regions,
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) -> Vec<Constrained<Rc<Frame>>> {
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// Layout child into padded regions.
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let pod = regions.map(|size| shrink(size, self.padding));
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let mut frames = self.child.layout(ctx, &pod);
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for ((current, base), Constrained { item: frame, cts }) in
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regions.iter().zip(&mut frames)
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{
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// Apply the padding inversely such that the grown size padded
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// yields the frame's size.
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let padded = grow(frame.size, self.padding);
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let padding = self.padding.resolve(padded);
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let offset = Point::new(padding.left, padding.top);
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// Grow the frame and translate everything in the frame inwards.
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let frame = Rc::make_mut(frame);
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frame.size = padded;
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frame.translate(offset);
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// Set exact and base constraints if the child had them. Also set
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// base if our padding is relative.
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let is_rel = self.padding.sum_by_axis().map(Linear::is_relative);
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cts.exact = current.filter(cts.exact.map_is_some());
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cts.base = base.filter(is_rel | cts.base.map_is_some());
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// Inflate min and max contraints by the padding.
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for spec in [&mut cts.min, &mut cts.max] {
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spec.as_mut()
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.zip(padding.sum_by_axis())
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.map(|(s, p)| s.as_mut().map(|v| *v += p));
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}
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}
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frames
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}
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}
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/// Shrink a size by padding relative to the size itself.
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fn shrink(size: Size, padding: Sides<Linear>) -> Size {
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size - padding.resolve(size).sum_by_axis()
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}
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/// Grow a size by padding relative to the grown size.
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/// This is the inverse operation to `shrink()`.
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///
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/// For the horizontal axis the derivation looks as follows.
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/// (Vertical axis is analogous.)
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///
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/// Let w be the grown target width,
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/// s be given width,
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/// l be the left padding,
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/// r be the right padding,
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/// p = l + r.
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///
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/// We want that: w - l.resolve(w) - r.resolve(w) = s
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///
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/// Thus: w - l.resolve(w) - r.resolve(w) = s
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/// <=> w - p.resolve(w) = s
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/// <=> w - p.rel * w - p.abs = s
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/// <=> (1 - p.rel) * w = s + p.abs
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/// <=> w = (s + p.abs) / (1 - p.rel)
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fn grow(size: Size, padding: Sides<Linear>) -> Size {
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size.zip(padding.sum_by_axis())
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.map(|(s, p)| (s + p.abs).safe_div(1.0 - p.rel.get()))
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}
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